Kepler data point to more planets in habitable zone

An artist's depiction of what sunset might look like on a moon of PH2… (H. Giguere, M. Giguere /…)

There could be a lot of Earth-like planets out there, new analysis of data from NASA's Kepler telescope suggests.

Speaking in Long Beach on Monday, at the annual meeting of the American Astronomical Society, NASA researchers working with the mission reported that they had discovered 461 new planet candidates -- four of which are less than two times the size of Earth and are located in their stars' so-called habitable zones, where liquid water might exist on smaller, rocky planets.

In other words: potentially the kinds of places where life could thrive.

The Kepler mission looks out at a vast field of more than 150,000 stars, scanning for the periodic dimming in their light that might indicate orbiting planets are crossing in front of them, also known as transiting.

So far, the NASA team said Monday, Kepler has detected 2,740 candidate planets orbiting 2,036 stars. Thus far, 105 of the candidates have been confirmed to be planets, they added.

The number of Earth-size and super-Earth size candidates -- planets up to two times the size of Earth -- grew sharply in the last year, they said. The count for Earth-size planet candidates is now 351, up 43%. There are 816 possible superearths, an increase of 21%. The number of stars that have more than one planet candidate in orbit around them also increased.

Also on Monday, the citizen scientist collaboration Planet Hunters, which recruits non-scientists to look over Kepler data after NASA researchers have taken their first crack at it, also reported finding 48 new planet candidates, including 15 in their stars' habitable zones. There's likely some overlap between the NASA count and Planet Hunters' tally. Still, said Meg Schwamb, a postdoctoral researcher at Yale University who works with the collaboration, the discoveries point toward a universe that could be teeming with Earths.

Planet Hunters also reported that one planet candidate in its portfolio had been confirmed to be a Jupiter-sized planet that orbits its sun-like host star every 282.5 days, at a distance of about .83 that between the sun and the Earth.

PH2 b, as the planet has been named, is the second to be confirmed by scientists working with the citizen scientists (for more on the first, see related story to the left.) Because it is a gas giant, it would not be suitable for life. But if it has moons, they could be hospitable worlds.

"Pandora could be sitting there," Schwamb said, referring to the fictional moon from the movie "Avatar," which orbited a giant planet.

Kepler scientists will present further details about their discoveries at the Long Beach conference on Tuesday.

Schwamb, who was attending the meeting, she said that she was particularly excited to hear about the new Kepler candidate KOI-172.01, which, with a radius around 1.5 times that of the Earth, may be the smallest planet candidate in the habitable zone of a Sun-like star.